JPS6024152B2 - liquid crystal composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Electrodes are formed on opposing surfaces of two substrates, and between the electrodes,
When a nematic liquid crystal composition is filled to form a transparent thin layer and a voltage is applied between the electrodes while allowing light to enter the nematic liquid crystal layer, the portion of the liquid crystal layer where the voltage is applied becomes cloudy. The phenomenon of blocking transparent light is known.

Using this phenomenon, light blocking devices that block light, display devices that display characters, numbers, symbols, figures, etc., have been manufactured.

In such devices, in order to increase the degree of cloudiness of the nematic liquid crystal layer or to speed up the response speed,
Various additives have been added to nematic liquid crystal materials. However, in liquid crystal compositions in which commonly used quaternary ammonium halide salts, carboxylic acid, phosphonium halide salts, and pyridium halide or sulfonate salts are added to nematic liquid crystals, the conductivity ( The temperature dependence (ratio of conductivity change with respect to temperature change) of current The disadvantage is that the power consumption increases.

By the way, in order to produce cloudiness, the conductivity of the liquid crystal system must be adjusted (
It is necessary to set it to a certain value or more determined by the value of (permittivity x driving frequency).

And the temperature dependence of conductivity is generally .

=0. It is expressed as exp (-ΔE/kT). however,
. : Electrical conductivity at temperature TK. .

o: Electrical conductivity at temperature K. △E: activation energy.

k: Holtmann constant.

T: Absolute temperature In the above conductivity equation, the minimum conductivity that effectively causes clouding in the liquid crystal system at 0°C by applying a certain voltage (25V, 60Hz) is approximately 10-loo-1 It is.

On the other hand, the electrical conductivity 〇 at any temperature T above 0°C is
The smaller the activation energy ΔE of conductivity, the smaller the temperature dependence, and unnecessary power consumption can be saved. On the other hand, in order to improve the contrast ratio between the light-scattering part and the non-scattering part, the orientation of the liquid crystal molecules is controlled when the orientation is below the threshold voltage of the clouding effect, and the long axis direction of the liquid crystal molecules is aligned regularly with the electrode substrate. It is necessary to arrange them vertically.

Conventionally, this vertical alignment method involves applying an alignment agent to the substrate surface, adding an alignment agent to the liquid crystal material, or treating the glass surface with acid to obtain uniform molecular alignment. However, these vertical alignment methods often result in changes in the conductivity of the liquid crystal and deterioration of the liquid crystal due to elution of the alignment agent applied to the substrate into the liquid crystal.

The present invention has been made in view of the above points.

J That is, the present invention:
To obtain a liquid crystal composition that has excellent response speed and degree of cloudiness, has little temperature dependence of conductivity (current), and furthermore has the most axial direction of liquid crystal molecules uniformly orthogonally aligned with respect to an electrode substrate. It was done for that purpose. As a result of intensive research, the present inventors added a type of salt consisting of a long-chain linear alkyl organic amine and an organic carboxylic acid to a nematic liquid crystal material as an additive (the amount added was 0.
05 weight percent to 3. (more preferably 0.1 to 2.5 weight percent)
As a result, the resulting liquid crystal composition is excellent in the degree of cloudiness and response speed, and has characteristics in which the temperature dependence of conductivity (current) is small.

In addition, liquid crystal compositions using the above additives have the property that the long axes of liquid crystal molecules spontaneously align perpendicularly to the substrate surface without the conventional alignment agent treatment. I found it. That is, the additive according to the present invention, which is a salt of a long mirror-like linear alkylamine and an organic carboxylic acid, has the structural formula C
It is expressed as nH2n+.

(X is an aliphatic hydrocarbon benzene ring or a substituted benzene ring)
This additive is a conductivity imparting agent that increases the cloudiness of liquid crystal.
In order to uniformly orient the liquid crystal molecules on the substrate, the constituent molecules, the most chained linear alkyl organic amines CnH2n+,
It is suitable that n=7 to 2 corm size.

In addition, the substituents R and R2 bonded to nitrogen are
1C2 day 5 or day 2 R,, R2 may be the same or different.

For example, primary amines such as n-dodecylamine and n-hexadecylamine.

Secondary amines such as N-methyloctylamine, N-ethyldodecylamine, and N-penzyldodecylamine. Tertiary amines such as N,N-dimethyloctylamine, N,N-dimethyldodecylamine, N,N-dimethylbentacosylamine, N,N-diethylhexadecylamine, and N-methylpenzyldodecylamine. on the other hand,
Among the organic carboxylic acids constituting this additive, one of them, an aliphatic carboxylic acid, has the structural formula CmH2m+, CO
It is expressed in O days, and n=1 to 6.

For example, monoaliphatic carboxylic acids such as acetic acid and propionic acid.

Another organic carboxylic acid, aromatic organic carboxylic acid, is represented by a structural formula.

(In the formula, X., X2, X3, X4, X5 are days, N〇2,
It is represented by CH3, 〇CH3, Br, CI.

) For example, unsubstituted benzoic acid such as benzoic acid, P-methylbenzoic acid, P-nitrobenzoic acid, P-frombenzoic acid,
Monosubstituted benzoic acids such as 0-methylbenzoic acid and m-chlorobenzoic acid. Disubstituted benzoic acids such as 3,5-dinitrobenzoic acid, 2,4-dinitrobenzoic acid, and 3,5-dimerbenzoic acid. The long-chain linear alkylamine and the organic carboxylic acid form a white or yellow salt.

However, when only long-chain linear alkylamine is added, it is difficult to obtain sufficient electrical conductivity, and when only organic carboxylic acid is added, it is difficult to uniformly align the long axes of liquid crystal molecules perpendicular to the substrate. Not only is this impossible, but it also promotes the decomposition of Schiff base liquid crystals having azomethine groups and ester liquid crystals having ester groups.

However, the additive according to the present invention, a salt of a long mirror-like linear alkylamine and an organic carboxylic acid, provides a sufficient clouding effect without promoting the decomposition of the liquid crystal material, and has little temperature dependence of conductivity. , provides a liquid crystal composition that promotes uniform vertical alignment of liquid crystal molecules.

The additive of the present invention has the effect of aligning the long axes of liquid crystal molecules perpendicularly to the substrate, and this is because long-chain linear alkyl organic amines and their proton adducts A hydrophobic film is formed on the surface of the glass substrate on which the liquid crystal is vapor-deposited, creating a so-called low-energy surface with a low critical surface tension, and the liquid crystal in contact with this is oriented in such a way as to reduce its own surface tension. Therefore, it is thought that the orientation is perpendicular to the interface.

The above additives may be any Nn-type nematic liquid crystal material (
This is effective for cases where the dielectric anisotropy value is negative.

For example, azoxy compounds such as P-azoxyanisole, ester compounds such as P-bentylphenyl-2-chloro-4-(P-bentylbenzoyloxy)penzoate, and P-alkoxybenzylidene-P-alkylaniline. It is effective against stilbene compounds such as Schiff compounds, P-alkyl, and P'-alkoxy-Q-chlorostilbenes. Next, the present invention will be specifically explained with reference to Examples.

First, a synthetic scheme for providing the above additive is shown below.

Example 1 Salt of N,N-dimethylalkylamine and organic carboxylic acid (Step 1) CmH2n+, NH2 10buri○12HC
OOH (n-alkylamine) (formaldehyde) (
Formic acid) (n = 8 to 25) ↓ Reflux 80 to 90008 hours Cn is n+, N (CH3) 20 is 20 tenth order 02 (N, N
-dimethylalkylamine (1)) (Step 2) (Salt of N,N-dimethylalkylamine and organic carboxylic acid) Example 2 N-methyl benzyl dodecyl amine and 3,5-dinitrobenzoic acid or 2,4- Salt of dinitrobenzoic acid (Step 1) n-dodecylamine (benzaldehyde) (N-penzylidene-n-dodecylamine) (〇) (Step 2) (N-penzylidene-n-dodecylamine) (m) (Step 3) (m) + Buri○ 10 2HCOOH (formaldehyde) (formic acid) (N-methyl benzyl n-dodecylamine) (W) (Step 4) Kamesaaki=;3; CnH2n+
, NH2 10 HOOC-X (n-alkylamine) (organic carboxylic acid) (salt of n-alkylamine and organic carboxylic acid) The synthesis process of each additive will be described below in the order of examples based on the above synthesis scheme.

Example 1 (Step 1) Ichihan formic acid (85-90%) 25.6 moles (=0.5 mol)
Cool with cold water and gradually add 0.1 mol of n-alkylamine.

Then, 22.5cc of formaldehyde (37%) (=
0.3 mol) and heated to 90-10,000 ℃. 2
Carbon dioxide is generated after ~3 minutes, during which time the temperature is returned to room temperature, and to stop the generation, the mixture is heated under reflux again at 90 to 100°C for 8 hours.

After cooling the reaction, add 50 cc of 4N hydrochloric acid, dry under reduced pressure, dissolve the residue (light yellow half-contained steel liquid) in 30 to 40 cc of water, add 25 cc of 18N sodium hydroxide, separate the oil layer, and dilute the water layer with benzene. N,N-dimethylalkylamine {1
). Table 1 below shows the boiling point and state of each N,N-dimethyl-n-alkylamine. (Step 2)
When equimolar amounts of each of the N,N-dimethyl n-alkylamine and organic carboxylic acid obtained in Table 1 are reacted in ethanol or acetone at 40 to 50 do for 1 hour, N,N-dimethyl-n-alkylamine and organic carboxylic acid are reacted. Salt is obtained.

The obtained salt of N,N-dimethyl, n-alkylamine and organic carboxylic acid is purified by a reprecipitation method from benzene-n-hexane.

Table 2 below shows the melting points and states of salts of N,N-dimethyl-n-alkylamines and organic carboxylic acids.

*By micro melting point measuring device K (Yanagimoto Seisakusho) Table 2 Examples. 2 (Step 1) 18.5 mol (=0.1 mol) of n-dodecylamine, 10.6 mol (=0.1 mol) of penzaldehyde, and a catalytic amount of acetic acid in absolute ethanol at 60-7000 ml for 4 hours. After the reaction, the ethanol is removed and the residue is distilled under reduced pressure to obtain an oily transparent substance N-penzylidene-n-dodecylamine (0) containing a low melting point solid.

Boiling point: 0.6 mm Hg 160-16 mm (Step 2) Dissolve 1.9 mmol of lithium aluminum hydride (=0.05 mole) in 80 cc of anhydrous tetrahydrofuran, and add the N- obtained above at room temperature. Penzylidene-n-dodecylamine is gradually added and the reaction is then carried out at 50 to 60°C for 1 hour to obtain N-benzylidene-n-dodecylamine (m).

This compound is purified by distillation. Boiling point 0.
6 Hg 150-157 CC (Step 3) Commercially available formic acid (85-90%) 8.96 mm (=0.105 mol) was cooled with cold water, and N-benzyl-n-dodecylamine 9.5 mm (=0 .035 mol) is added.

Then formaldehyde (37%) 2.4cc (=0.
0525 mol) and heat to 90-100oo.
After a few minutes, carbon dioxide is generated, so the temperature is returned to room temperature during that time, and to stop the generation, the mixture is heated under reflux again at 90 to 1000 C for 8 hours. After cooling the reaction, 18 cc of 4N hydrochloric acid was added and the mixture was dried under reduced pressure. Dissolve the residue in 5 cc of water, add 10 cc of 18N sodium hydroxide, separate the oil layer, extract the aqueous layer with benzene, distill off the benzene, and vacuum distill the residue to obtain N-methyl benzene dodecylamine (W). ). Boiling point 0.4 Hg 146-14900 (Step 4) Equimolar amounts of each of the obtained N-methylbenzyl-n-dodecylamine and 3,5-dinitrobenzoic acid or 2,4-dinitrobenzoic acid were dissolved in ethanol or acetone. 40-5
When reacted for 1 hour at 0qo, N-methyl benzyl,
n-dodecylamine and a salt of 3,5-dinitrobenzoic acid or N-methylpenzyl-n-dodecylamine and 2,
A salt of 4-dinitrobenzoic acid is obtained.

Table 3 below shows the state of each salt.

Table 3 Example 3 n-alkylamine CnH 10, NH2 (n 8~2
5) and an organic carboxylic acid in acetone.
When reacted at 5 to 400C for 1 hour, a salt of n-alkylamine and organic carboxylic acid is obtained.

These salts can be purified from benzene-n-hexane by a reprecipitation method. Table 4 below shows the melting point and state of each salt.

*Kuyanagimoto Seisakusho using a micro-melting point measuring device) Table 4 Next, examples of results obtained when the electrical properties of nematic liquid crystals are controllably changed using the above-mentioned additives according to the present invention are shown.

Example 4 A nematic liquid crystal mixture is prepared by mixing various liquid crystal substances in the proportions shown in Table 5 below.

The above liquid crystal temperature is -16°C to 63°C. Prepare two glass plates with transparent electrodes made of indium on their surfaces, and arrange the two glass plates in parallel with the transparent electrodes on the inside. A transmissive liquid crystal cell with a distance between electrodes of 20 mm was fabricated.

Next, the above-mentioned liquid crystal mixture and an additive (tetrabutylammonium) commonly used in the above-mentioned liquid crystal mixture are added.

A transparent thin layer is formed by filling the above-mentioned cell with a liquid crystal composition to which a liquid crystal composition is added, and a liquid crystal composition to which various additives according to the present invention are added in various proportions. z, an alternating current voltage of 25 V was applied, and the current flowing therebetween, response speed, threshold voltage, and light transmittance were measured, and the results shown in Table 6 were obtained. In addition, temperature dependence was examined in the same manner, and the results shown in Table 7 and FIG. 1 were obtained.

0 Figure 1 shows a liquid crystal composition in which 0.05% by weight of 3.5-dinitrobenzoate of tetrabutylammonium, which has been conventionally used, is added to the liquid crystal mixture shown in Table 5. Additives N,N-dimethyl-n-octylamine and the salt of 3,5 dinitrobentazoic acid were added to 0. Curve B shows the liquid crystal composition containing 0.0% of the base weight, and 0.0% of the salt of N,N-dimethyl-n-dodecylamine and 3,5-dinitrobenzoic acid. Curve C shows a liquid crystal composition to which 1.0 weight % of N,N-dimethyl-n-dodecylamine and 2,4-dinitrobenzoic acid are added.
N,N-dimethyl-n-hexadecylamine and 3,5-
1. salt of dinitobenzoic acid. Curve E shows a liquid crystal composition to which 1.5% by weight of a salt of N,N-dimethyl-n-hexadecylamine and 2,4-dinitrobenzoic acid has been added, and curves F, N, N-methylbenzyl-n
1 salt of dodecylamine and 3,5-dinitrobenzoic acid
．． Curve G shows the liquid crystal composition containing 0.0% by weight of a salt of n-dodecylamine and 3,5-dinitrobenzoic acid. Standing weight%
The added liquid crystal compositions are each expressed in terms of curve days, and the temperature dependence of conductivity is shown.

Example 5 A transparent electrode made of indium oxide was coated with a silicon oxide vapor-deposited film (
Deposition conditions: substrate temperature 350qo, vacuum degree 7×10-4T
Prepare two glass plates covered with 02 leak (02 leak), speed 1 to 1.5 A/sec, film thickness 500 A), and place the two glass plates in parallel with indium oxide silicon monoxide on the inside. In the meantime, the liquid crystal mixture, a liquid crystal composition prepared by adding a conventionally commonly used additive (3.5 dinitrobenzoate of tetrabutylammonium), and various additives according to the present invention are added to the liquid crystal mixture. A liquid crystal composition added at a ratio of 100 to 100% was filled, and the perpendicular orientation of the liquid crystal was examined using crossed Nichols, and the results shown in Table 8 were obtained.

Measurement conditions: 25V, 60Hz, 20〃m, 25℃ sine wave *: Values in vertical orientation Table 6 Table 7 Measurement conditions: 25V, 60Hz, 20〃m Sine wave: Homogeneous (horizontal) orientation -- : Homeotropic (vertical) alignment As is clear from Table 8, Table 6, the additives of the present invention, a salt of a chain-shaped alkyl organic amine and an organic carboxylic acid, are added to the liquid crystal mixture shown in Table 5 above. By doing so,
The current value, transmittance, response speed, time threshold voltage of the liquid crystal composition can be significantly improved as compared to the case of no additive or the case of using conventionally used additives.

Moreover, as is clear from Table 7 and FIG. 1, compared to the conventional 3,5-dinitrobenzoate of tetrabutylammonium, the long-chain straight mirror alkylamine and organic carboxylamine, which are the additives according to the present invention, By adding an acid salt, it was possible to reduce the temperature dependence of conductivity. In other words, the equation for the temperature dependence of conductivity.

=〇. Comparing △E at exp (1△E/kT) with the conventional example, 0. It was possible to lower the gold V to 0.32 to 0.4 tomo V.

As shown in Table 7, the rate of increase in current (current at 4000°C/current at 0°C) is approximately 1/4.8 compared to the conventional example.
I was able to reduce it to 1/2.9 bases. In this way, the temperature dependence of the current value is small, which means that if the minimum operating temperature is 0°C and the current is, for example, 5.0 French A/(25 V, about 60, d = 20 French m), it will be 0° C. In the high temperature range above, for example, 4000, in the conventional example 131.5 French A/C boat (2
5V, 60Hz, cell thickness 20m), and the liquid crystal composition of the present invention has a voltage of 27.5 to 58.3A/(25V, 60m).
0 Hz, cell thickness 20 m), and has the advantage of being able to drive a liquid crystal display with low power consumption. Furthermore, the eighth
As is clear from the table, compared to the conventional additive 3.5 dinitrobenzoate of tetrabutylammonium,
It has been found that the additive according to the present invention has the effect of uniformly aligning the long axis direction of liquid crystal molecules perpendicular to the substrate surface.

The fact that the additive according to the present invention has the property of promoting perpendicular alignment means that it is possible to uniformly align liquid crystal molecules without applying an alignment agent to the substrate surface or adding a separate alignment agent to the liquid crystal mixture. It has the advantage of being able to be arranged regularly.

As explained in detail above, according to the present invention, the response speed, the reduction of the temperature dependence of current value, and the improvement of the clouding effect when voltage is applied, as well as the additive as an ion additive,
It also has properties as a vertical alignment agent.

[Brief explanation of the drawing]

The drawing is a diagram showing a comparison of conductivity change characteristics with respect to temperature between a conventional liquid crystal composition and a liquid crystal composition of the present invention. A is a characteristic curve of the conventional example, and B~ days are characteristic curves of each embodiment of the present invention.

Claims (1)

[Claims] 1. A nematic material comprising, as an additive, at least one salt selected from the group consisting of a long-chain linear alkyl organic amine in which at least one H atom is bonded to a N atom and a salt of an organic carboxylic acid. liquid crystal composition.